Method and system for extraction of hydrocarbons from oil shale and limestone formations

ABSTRACT

A system and method for extracting hydrocarbon products from limestone using nuclear energy sources for energy to fracture the limestone formations and provide sufficient heat and pressure to produce liquid and gaseous hydrocarbon products. Embodiments of the present invention also disclose steps for extracting the hydrocarbon products from the limestone formations.

CROSS REFERENCE TO RELATED APPLICATIONS

This patent application is a continuation-in-part of U.S. patentapplication Ser. No. 11/600,992, filed on Nov. 17, 2006 andInternational Patent Application No. PCT/US07/04852, filed on 23 Feb.2007. U.S. patent application Ser. No. 11/600,992 claims the benefit ofU.S. Provisional Patent Application Ser. No. 60/765,667, filed on Feb.6, 2006 and International Patent Application No. PCT/US07/04852 claimsthe benefit of U.S. Provisional Patent Application Ser. No. 60/766,435,filed on Feb. 24, 2006, the contents of each of these references beingincorporated herein by reference in their entireties.

FIELD OF THE INVENTION

The present invention relates to using alternative energy sources tocreate a method and system that minimizes the cost of producing useablehydrocarbons from hydrocarbon-rich shales or “oil shales” and“limestone” geologic formations. The advantageous design of the presentinvention, which includes a system and method for the recovery ofhydrocarbons, provides several benefits including minimizing energyinput costs, limiting water use and reducing the emission of greenhousegases and other emissions and effluents, such as carbon dioxide andother gases and liquids.

BACKGROUND OF THE INVENTION

Discovery of improved and economical systems and methods for extractinghydrocarbons from organic-rich rock formations, such as oil shale andlimestone formations, has been a challenge for many years. Historically,a substantial amount of hydrocarbons are produced from subterraneanreservoirs.

The reservoirs can include organic-rich shale and limestone formationsfrom which the hydrocarbons derive. The shale contains a hydrocarbonprecursor known as kerogen. Kerogen is a complex organic material thatcan mature naturally to hydrocarbons when it is exposed to temperaturesover 100° C. This process, however, can be extremely slow and takesplace over geologic time.

Immature oil shale formations are those that have yet to liberate theirkerogen in the form of hydrocarbons. These organic rich rock formationsrepresent a vast untapped energy source. The kerogen, however, must berecovered from the oil shale formations, which under prior known methodscan be a complex and expensive undertaking, which may have a negativeenvironmental impact such as greenhouse gases and other emissions andeffluents, such as carbon dioxide and other gases and liquids.

In a known method, kerogen-bearing oil shale near the surface can bemined and crushed and, in a process known as retorting, the crushedshale can then be heated to high temperatures to convert the kerogen toliquid hydrocarbons. There are, however, a number of drawbacks tosurface production of shale oil including high costs of mining,crushing, and retorting the shale and a negative environmental impact,which also includes the cost of shale rubble disposal, site remediationand cleanup. In addition, many oil shale deposits are at depths thatmake surface mining impractical.

In other methods, oil occurs in certain geologic formations at varyingdepths in the earth's crust. In many cases elaborate, expensiveequipment is required for recovery. The oil is usually found trapped ina layer of porous sandstone, which lies beneath a dome-shaped or foldedlayer of some non-porous rock such as limestone. In other formations,the oil is trapped at a fault, or break in the layers of the crust.

In the dome and folded formations of the limestone, natural gas isusually present below the non-porous layer and immediately above theoil. Below the oil layer, the sandstone is usually saturated with saltwater. The oil is released from this formation by drilling a well andpuncturing the limestone layer on either side of the limestone dome orfold.

Attempts have been made to overcome the drawbacks of prior known methodsof recovery by employing in situ (i.e., “in place”) processes. In situprocesses can include techniques whereby the kerogen in oil shale issubjected to in situ heating through combustion, heating with othermaterial or by electric heaters and radio frequencies in the shaleformation itself. The shale is retorted and the resulting oil drained tothe bottom of the rubble such that the oil is produced from wells. Instill other attempts, in situ techniques have been described thatinclude fracturing and heating the shale formations and limestoneformations underground to release gases and oils. These types oftechniques typically require finished hydrocarbons to produce thermaland electric energy and heat the shale and limestone formations, and mayemploy conventional hydro-fracturing techniques or explosive materials.These attempts, however, also continue to suffer from disadvantages suchas negative environmental impacts, high fuel costs to produce thermalenergy for heating and/or electricity, as well as high waterconsumption. In addition, these methods may have a negativeenvironmental impact such as greenhouse gases and other emissions andeffluents, such as carbon dioxide and other gases and liquids.

Therefore, it would be desirable to overcome the disadvantages anddrawbacks of the prior art with a method and system for recoveringhydrocarbon products from rock formations, such as oil shale andlimestone formations, which fracture the formation and heat the oilshale and/or limestone via thermal or electrically induced energyproduced by a nuclear reactor. It would be desirable if the method andsystem can accelerate the maturation process of the precursors of crudeoil and natural gas. It is most desirable that the method and system ofthe present invention is advantageously employed to minimize energyinput costs, limit water use and reduce the emission of greenhouse gasesand other emissions and effluents, such as carbon dioxide and othergases and liquids.

SUMMARY OF THE INVENTION

Accordingly, a method and system is disclosed for recovering hydrocarbonproducts from rock formations, such as oil shale and limestoneformations, which fracture the formation and heat the oil shale and/orlimestone via thermal energy produced by a nuclear reactor forovercoming the disadvantages and drawbacks of the prior art. Desirably,the method and system can accelerate the maturation process of theprecursors of crude oil and natural gas. The method and system may beadvantageously employed to minimize energy input costs, limit water useand reduce the emission of greenhouse gases and other emissions andeffluents, such as carbon dioxide and other gases and liquids. It isenvisioned that the enhanced fracturing technologies disclosed cangreatly increase the efficiency of producing oil from these limestoneformations.

In the method and system it is contemplated that supercritical materialwill be injected into the oil shale and/or limestone formations toproduce fracturing and porosity that will maximize the production ofuseful hydrocarbons from the oil shale formation and limestoneformations.

In one particular embodiment, in accordance with the present disclosure,a method for recovering hydrocarbon products is provided. The methodincludes the steps of: producing thermal energy using a nuclear reactor;providing the thermal energy to a hot gas generator; providing a gas tothe hot gas generator; producing a high pressure hot gas flow from thehot gas generator using a high pressure pump; injecting the highpressure hot gas flow into injection wells wherein the injection wellsare disposed in a limestone formation; retorting limestone in thelimestone formation using heat from the hot gas flow to producehydrocarbon products; and extracting the hydrocarbon products from therecovery well. It is contemplated that the method, and the alternativeembodiments discussed, include the injection wells, which may bedisposed in rock formations that include oil shale and limestone,whereby oil shale and limestone is retorted. It is further contemplatedthat such rock formations only include oil shale.

In an alternate embodiment, the method includes the steps of: generatingelectricity using a nuclear powered steam turbine; retorting limestonein a limestone formation using electric heaters powered by theelectricity to produce hydrocarbon products; and extracting thehydrocarbon products from the injection well.

In another alternate embodiment, the method includes the steps of:producing thermal energy using a nuclear reactor; providing the thermalenergy to a molten salt or liquid metal generator; providing a salt ormetal to the molten salt or liquid metal generator; producing a moltensalt or liquid metal flow from the molten salt or liquid metal generatorusing a pump; injecting the molten salt or liquid metal flow intobayonet injection wells wherein the injection wells are disposed in alimestone formation; retorting limestone in limestone formation usingheat from the molten salt or liquid metal flow to produce hydrocarbonproducts; and extracting the hydrocarbon products from the recoverywell.

In another alternate embodiment, the method includes the steps of:generating electricity using a nuclear powered steam turbine; retortingin a limestone formation using radio frequencies powered by theelectricity to produce hydrocarbon products; and extracting thehydrocarbon products from the recovery well.

The present invention provides a system and method for extractinghydrocarbon products from oil shale and/or limestone formations usingnuclear reactor sources for energy to fracture the oil shale formationsand/or limestone formations and provide sufficient heat and/or electricpower to produce liquid and gaseous hydrocarbon products. Embodiments ofthe present invention also disclose steps for extracting the hydrocarbonproducts from the oil shale and/or limestone formations.

Oil shale and limestone contain the precursors of crude oil and naturalgas. The method and system can be employed to artificially speed thematuration process of these precursors by first fracturing the formationusing supercritical materials to increase both porosity andpermeability, and then heat the shale and/or limestone to increase thetemperature of the formation above naturally occurring heat created byan overburden pressure. The use of a nuclear reactor may reduce energyinput cost as compared to employing finished hydrocarbons to producethermal energy and/or electricity. Nuclear reactors produce thesupercritical temperature in the range from 200° to 1100° C. (dependingon the material to be used) necessary for increasing the pressure usedin the fracturing process compared to conventional hydro fracturingand/or the use of explosives. In oil shale and limestone formations, themaximization of fracturing is advantageous to hydrocarbon accumulationand recovery. Generally, massive shales and limestone formations intheir natural state have very limited permeability and porosity.

In addition, limiting water use is also beneficial. The use of largequantities of water has downstream implications in terms of wateravailability and pollution. The method and system may significantlyreduce water use.

Further, the use of natural gas/coal/oil for an input energy sourcecreates greenhouse gases and other emissions and effluents, such ascarbon dioxide and other gases. An increasingly large number of earthscientists believe that greenhouse gases contribute to a phenomenonpopularly described as “global warming”. The method and system of thepresent disclosure can significantly reduce the emission of greenhousegases.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention, both as to its organization and manner ofoperation, will be more fully understood from the following detaileddescription of illustrative embodiments taken in conjunction with theaccompanying drawings in which:

FIG. 1 is a schematic diagram of a method and system for fracturing oilshale and/or limestone formations using a nuclear energy source inaccordance with the principles of the present invention;

FIG. 2 is a schematic diagram of directionally drilled shafts used at anextraction site, in accordance with the principles of the presentinvention;

FIG. 3 is a process energy flow diagram of the method and system shownin FIG. 1;

FIG. 4 is a schematic diagram of a method and system for retorting oilshale and/or limestone using a nuclear energy source in accordance withthe principles of the present invention;

FIG. 5 is a process energy flow diagram of the method and system shownin FIG. 4;

FIG. 6 is a schematic diagram of an alternate embodiment of the methodand system shown in FIG. 4;

FIG. 7 is a process energy flow diagram of the method and system shownin FIG. 6;

FIG. 8 is a schematic diagram of an alternate embodiment of the methodand system shown in FIG. 4;

FIG. 9 is a process energy flow diagram of the method and system shownin FIG. 8;

FIG. 10 is a schematic diagram of an alternate embodiment of the methodand system shown in FIG. 4; and

FIG. 11 is a process energy flow diagram of the method and system shownin FIG. 10.

DETAILED DESCRIPTION

The exemplary embodiments of the method and system for extractinghydrocarbon products using alternative energy sources to fracture oilshale formations and/or limestone formations and heat the oil shaleand/or limestone to produce liquid and gaseous hydrocarbon products arediscussed in terms of recovering hydrocarbon products from rockformations and more particularly, in terms of recovering suchhydrocarbon products from the oil shale and limestone formations viathermal energy produced by a nuclear reactor. The method and system ofrecovering hydrocarbons may accelerate the maturation process of theprecursors of crude oil and natural gas. It is contemplated that such amethod and system as disclosed herein can be employed to minimize energyinput costs, limit water use and reduce the emission of greenhouse gasesand other emissions and effluents, such as carbon dioxide and othergases and liquids. The use of a nuclear reactor to produce thermalenergy reduces energy input costs and avoids reliance on finishedhydrocarbon products to produce thermal energy and the related drawbacksassociated therewith and discussed herein. It is envisioned that thepresent disclosure may be employed with a range of recovery applicationsfor oil shale and/or limestone extraction including other in situtechniques, such as combustion and alternative heating processes, andsurface production methods. It is further envisioned that the presentdisclosure may be used for the recovery of materials other thanhydrocarbons or their precursors disposed in subterranean locations.

The following discussion includes a description of the method and systemfor recovering hydrocarbons in accordance with the principles of thepresent disclosure. Alternate embodiments are also disclosed. Referencewill now be made in detail to the exemplary embodiments of the presentdisclosure, which are illustrated in the accompanying figures. Turningnow to FIG. 1, there is illustrated a method and system for recoveringhydrocarbon products, such as, for example, a system 20 for fracturingand retorting oil shale and/or limestone using a nuclear reactor and anassociated thermal transfer system, in accordance with the principles ofthe present disclosure.

The nuclear reactor and thermal components of system 20 are suitable forrecovery applications. Examples of such nuclear reactor and thermalcomponents are provided herein, although alternative equipment may beselected and/or preferred, as determined by one skilled in the art.

Detailed embodiments of the present disclosure are disclosed herein,however, it is to be understood that the described embodiments aremerely exemplary of the disclosure, which may be embodied in variousforms. Therefore, specific functional details disclosed herein are notto be interpreted as limiting, but merely as a basis for the claims andas a representative basis for teaching one skilled in the art tovariously employ the present disclosure in virtually any appropriatelydetailed embodiment.

In one aspect of system 20 and its associated method of operation, alimestone extraction site 22 is selected for recovery of hydrocarbonproducts and treatment of the precursors of oil and gas. It isenvisioned that system 20 and its associated method, and the alternateembodiments discussed below, may be employed with an extraction site,which includes oil shale and limestone formations for recovery ofhydrocarbon products and precursors. It is further envisioned that suchan extraction site may only include oil shale formations.

Site selection will be based on subsurface mapping using existingborehole data such as well logs and core samples and ultimately datafrom new holes drilled in a regular grid. Areas with higherconcentrations of relatively mature kerogen, and limestone formationsand lithology favorable to fracturing will be selected. Geophysical welllog data where available, including resistivity, conductivity, soniclogs and so on will be employed. Seismic data is desirable; however,core analysis is a reliable method of determining actual porosity andpermeability which is related to both efficient heating and extractionof the end product, usable hydrocarbons. Grain size and distribution isalso desirable. Areas where there is high drilling density and reliabledata with positive indications in the data would be ideal. Geochemicalanalysis is also desirable to the process as limestone formations tendto have very complicated geochemical characteristics. Surfacegeochemistry is desirable in a localized sense. Structural features anddepositional environments are desirable in a more area or regionalsense. Reconstruction of depositional environments and post-depositionaldynamics are desirable. Three dimensional computer modeling providedthere is enough accurate data would be desirable. As experience isgained in the optimal parameters for exploitation, the entire processand system can be modulated in its application to different sub-surfaceenvironments.

At selected site 22, a surface level 24 is drilled for extraction ofcore samples (not shown) using suitable drilling equipment for a rockformation application, as is known to one skilled in the art. The coresamples are extracted from site 22 and geological information is takenfrom the core samples. These core samples are analyzed to determine ifsite 22 selected is suitable for recovery of hydrocarbons and treatmentof the precursors of oil and gas.

If the core samples have the desired characteristics, site 22 will bedeemed suitable for attempting to extract hydrocarbons from limestoneformations. Alternatively, site 22 may be deemed suitable for extractionof limestone and oil shale, or oil shale only. Accordingly, a strategyand design is formulated for constructing fracturing wells and retortinjection wells, as will be discussed below. Joints, fractures anddepositional weaknesses will be exploited in order to maximize theeffect of this method of fracturing. Ideally areas can be identifiedwhich have experienced a relatively higher degree of naturally occurringfracturing due to folding and faulting as observed in the coastal areasof central California. Piping arrays will be oriented in concert withthese existing weaknesses in order to create the maximum disruption ofthe rock matrix. The nuclear reactor placement will also be formulatedand planned for implementation, as well any other infrastructureplacements necessary for implementation of the system and method. It iscontemplated that if the core samples taken from the selected site arenot found to have the desired characteristics, an alternate site may beselected. Site 22 is also prepared for installation and relatedconstruction of a supercritical material generator 28 and othercomponents including high pressure pumps 30 and drilling equipment (notshown).

In another aspect of system 20, installation and related construction ofnuclear reactor 26 and the components of the thermal transfer system atsite 22 is performed. Plumbing equipment (not shown) is constructed andinstalled. A material supply 34 is connected to the plumbing equipmentand the components of the thermal transfer system. Electrical equipment(not shown) is wired and installed. Off-site electric connections (ifavailable) are made to the electrical equipment. If off-site electricconnections are not available, then a small stream of energy from thenuclear reactor may be generated using a conventional electric generator(not shown). It is contemplated that plumbing equipment and electricalequipment are employed that are suitable for an oil shale and/orlimestone formation extraction application and more particularly, forrecovery of hydrocarbons and treatment of their precursors, as is knownto one skilled in the art.

It is envisioned that nuclear reactor 26 may be a small or large scalenuclear reactor employed with system 20 in accordance with theprinciples of the present disclosure. Nuclear reactor 26 is a thermalsource used to provide thermal energy 32 to fracture an oil shaleformation and/or limestone formations (not shown). Nuclear reactor 26 issized to be located at or near the oil shale formation and/or limestoneformations of site 22. It is envisioned that the thermal rating ofnuclear reactor 26 is between 20 MWth to 3000 MWth. For example, anuclear reactor, such as the Toshiba 4S reactor, may be used. Thesereactors can include all generation III, III+ and IV reactors, includingbut not limited to Pressurized Water Reactors, Boiling Water Reactors,CANDU reactors, Advanced Gas Reactors, ESBWR, Very High TemperatureReactors, helium or other gas cooled reactors, liquid sodium cooledreactors, liquid lead cooled rectors or other liquid metal cooledreactors, molten salt reactors, Super Critical Water Reactors, and allnext generation nuclear plant designs.

Supercritical material generator 28 is constructed and installed at site22. Nuclear reactor 26 is coupled to supercritical material generator28, as is known to one skilled in the art, for the transfer of thermalenergy 32. Material supply source 34 delivers material 35 tosupercritical material generator 28. System 20 employs supercriticalmaterial generator 28, in cooperation with nuclear reactor 26 as thethermal source, to produce supercritical material 36 for fracturing oilshale formations and/or limestone formations. It is contemplated that anumber of materials may be generated by supercritical material generator28 for fracturing, such as water, carbon dioxide and nitrogen, amongothers.

The use of supercritical material 36 is employed to enhance permeabilityand porosity of an oil shale formation and/or limestone formationsthrough fracturing. Studies have shown that supercritical material canbe effectively used to permeate and fracture rock formations. (See,e.g., 14th International Conference on the Properties of Water and Steamin Kyoto, Sergei Fomin*, Shin-ichi Takizawa and Toshiyuki Hashida,Mathematical Model of the Laboratory Experiment that Simulates theHydraulic Fracturing of Rocks under Supercritical Water Conditions,Fracture and Reliability Research Institute, Tohoku University, Sendai980-8579, Japan), which is incorporated herein in its entirety. Othersupercritical material has been used in other applications.

Systems to manage the extremely high pressures must be installed inorder to safely operate the entire apparatus. Placement of blowoutpreventers and pressure relief valves will be integrated into the systemand carefully monitored particularly at the outset of testing theprocess.

High pressure pumps 30 are installed at site 22 and coupled tosupercritical material generator 28 for injecting supercritical material36 into the limestone formations. High pressure pumps 30 deliversupercritical material 36 to the limestone formations fracturing wells38 at high pressure. Supercritical material 36 is delivered at highpressures to the limestone formations to achieve maximum permeabilitytherein. It is envisioned that high pressure pumps 30 deliver pressuresin the range between 50 and 500 MPa or higher. These pumps may becentrifugal or other types of pumps. The high pressure pumps andrequired remote pumping stations (not shown) may be designed for remoteoperation using the pipeline SCADA (Supervisory Control And DataAcquisition) systems and may be equipped with protection equipment suchas intake and discharge pressure controllers and automatic shutoffdevices in case of departure from design operating conditions.Alternatively, pumps 30 may be installed at site 22 having limestone andoil shale formations, or only oil shale.

It is further envisioned that an optimal injection parameters can bedetermined based on the formation characteristics and other factors.Geologic environments can vary locally and regionally. As well asdiscussed above, system 20 may include various high pressure pumpconfigurations such as a series of multiple pumps to achieve optimalresults. The described supercritical material distribution system isconstructed and installed at site 22, as is known to one skilled in theart. All systems are tested and a shakedown integration is performed.

An infrastructure 39 for fracturing wells 38 (FIG. 1) is constructed atsite 22, as shown in FIG. 2. A drilling rig 40 with equipment designedfor accurate directional drilling is brought on site. It will be veryimportant to accurately determine the location of the bit whiledrilling. Many recent innovations in rig and equipment design make thispossible. Rigs may be leased on a day or foot rate and are brought inpiece by piece for large rigs and can be truck mounted for small rigs.Truck mounted rigs can drill to depths of 2200 feet or more 24 of site22, as is known to one skilled in the art. Drilling rig 40 is disposedadjacent a vertical drill hole 42 from which horizontal drill holes 44,which may be disposed at orthogonal, angular or non-orthogonalorientations relative to vertical drill hole 42, are formed. Limestoneformation fracturing wells 38 are installed with infrastructure 39 ofsite 22. Limestone formation fracturing wells 38 inject supercriticalmaterial 36 into drill holes 42, 44 of the limestone formation and site22. Alternatively, wells 38 may be configured for limestone and oilshale formations, or only oil shale.

Directional drilling is employed to maximize the increase inpermeability and porosity of the oil shale formation and/or limestoneformations and maximize the oil shale formation and/or limestoneformation's exposure to induced heat. The configuration of horizontaldrill holes 44 can be formulated based on geological characteristics ofthe oil shale formation and limestone formations as determined by coredrilling and geophysical investigation. These characteristics includedepositional unconformities, orientation of the bedding planes,schistosity, as well as structural disruptions within the formations asa consequence of tectonics. Existing weaknesses in the oil shaleformations and/or limestone formations may be exploited includingdepositional unconformities, stress fractures and faulting.

An illustration of the energy flow of system 20 for the limestoneformations fracturing operations (FIG. 1), as shown in FIG. 3, includesnuclear energy 46 generated from nuclear reactor 26. Nuclear energy 46creates thermal energy 32 that is transferred to supercritical materialgenerator 28 for producing supercritical material 36. Supercriticalmaterial 36 is delivered to high pressure pumps 30. Pump energy 48 putssupercritical material 36 under high pressure.

High pressure pumps 30 deliver supercritical material 36 to fracturingwells 38 with sufficient energy 50 to cause fracturing in the limestoneformations. Such fracturing force increases porosity and permeability ofthe limestone formations through hydraulic stimulation undersupercritical conditions. Residual supercritical materials from thefracturing operations are recovered via a material recovery system 45and re-introduced to supercritical material generator 28 via materialsupply 34 using suitable conduits, as known to one skilled in the art.It is envisioned that a material recovery system is employed to minimizethe consumption of material used to fracture the limestone formations. Arecycling system may be deployed in order to also minimize anygroundwater pollution and recycle material where possible.

In another aspect of system 20, the fracturing operations employing thesupercritical material distribution system described and limestoneformations fracturing wells 38 are initiated. Nuclear reactor 26 and thematerial distribution system are run. Fracturing of the limestoneformations via wells 38 is conducted to increase permeability andporosity of the limestone formations for heat inducement. The fracturingprocess in the limestone formation at site 22 is tracked via readingstaken. Based on these reading values, formulations are conducted todetermine when the fracturing is advanced to a desired level. One methodof determining the level of fracturing would be take some type ofbasically inert material, circulate it downhole, and read the amount andrate of material loss. In other words, measure the “leakage” into theformation. Gases may also be employed with the amount of pressure lossbeing used to measure the degree of fracturing. These measurements wouldbe compared to “pre-fracturing” level. This method would be particularlyhelpful in the case of microfracturing. Core samples are extracted fromthe fractured limestone formations. These samples are analyzed. Theanalysis results are used to formulate and plan for implementation of adrilling scheme for the injection wells for retort and perforation wellsfor product recovery. Alternatively, the discussed fracturing operationsmay be employed with limestone and oil shale formations, or only oilshale.

In another aspect of system 20, limestone fracturing wells 38 aredismantled from infrastructure 39. Initially, operation of nuclearreactor 26 is temporarily discontinued in cold or hot shutdown dependingon the particular reactor's characteristics. Limestone formationsfracturing wells 38 are dismantled and removed from infrastructure 39 ofsite 22. Retort wells and perforation recovery wells (not shown) areconstructed with infrastructure 39, in place of the limestone formationsfracturing wells 38, and installed at site 22 for connection with drillholes 42, 44. Exemplary embodiments of retort systems for use withsystem 20, in accordance with the principles of the present disclosure,will be described in detail with regard to FIGS. 4-11 discussed below.

The retort wells transfer heated materials to the fractured limestoneformations for heat inducement. The exposure of the limestone to heat inconnection with high pressure accelerates the maturation of thehydrocarbon precursors, such as kerogen, which forms liquefied andgaseous hydrocarbon products. In limestone formations, oil can beextracted using conventional techniques. During the retort operations,hydrocarbons accumulate. A suitable recovery system is constructed forhydrocarbon recovery, as will be discussed. Nuclear reactor 26 isrestarted for retort operations, as described. All systems are testedand a shakedown integration is performed.

In another aspect of system 20, the retort operations employing theretort wells and perforation recovery wells are initiated for productrecovery. The retort wells and the perforation wells are run andoperational. In one particular embodiment, as shown in FIG. 4, system 20includes a retort system 120 for retort operations relating to thefractured limestone formations at site 22, similar to that describedwith regard to FIGS. 1-3. Site 22 is prepared for installation andrelated construction of retort system 120, which includes gas handlingequipment and thermal transfer system components, which will bedescribed.

Retort system 120 employs hot gases that are injected into the fracturedlimestone formations to induce heating and accelerate the maturationprocess of hydrocarbon precursors as discussed. Nuclear reactor 26discussed above, is a thermal source that provides thermal energy 132 toretort the limestone formation in-situ. Nuclear reactor 26 is sized tobe located at or near site 22 of the fractured limestone formation. Itis envisioned that the thermal rating of nuclear reactor 26 is between20 MWth to 3000 MWth. It is further contemplated that hydrogen generatedby nuclear reactor 26 can be used to enhance the value of carbon bearingmaterial, which may resemble char and be recoverable. A hydrogengenerator (not shown), either electrolysis, thermal or other may beattached to the nuclear reactor 26 to generate hydrogen for this use.Alternatively, the retort wells and recovery wells may be employed withlimestone and oil shale formation applications, or only oil shale.

A gas injection system 134 is installed at site 22. Gas injection system134 delivers gas to a hot gas generator 128. Hot gas generator 128 isconstructed and installed at site 22. There are many types of hot gasgenerators available for this type of application including, but notlimited to boilers and the like. Nuclear reactor 26 is coupled to hotgas generator 128, as is known to one skilled in the art, for thetransfer of thermal energy 132. System 20 employs hot gas generator 128,in cooperation with nuclear reactor 26 as the thermal source, to producehot gas 136 for retort of the fractured limestone formations.

It is envisioned that the thermal output of nuclear reactor 26 can beused to heat various types of gases for injection to retort the oilshale and/or limestone formations such as air, carbon dioxide, oxygen,nitrogen, methane, acetic acid, steam or other appropriate gases otherappropriate combinations. Other gases can also be injected secondarilyto maximize the retort process if appropriate.

High pressure pumps 130 are installed at site 22 and coupled to hot gasgenerator 128 for injecting hot gas 136 into the fractured limestoneformations. High pressure pumps 130 put hot gas 136 into a high pressurestate to promote the retort of the limestone formations. It isenvisioned that system 20 may include various high pressure pumpconfigurations including multiple pumps and multiple gases to maximizethe effectiveness of the retort operation.

Limestone asset heating retort injection wells 138 are installed withthe infrastructure of system 20, as discussed. Hot gas 136 istransferred to injection wells 138 and injected into the fracturedlimestone formation. The use of horizontal drilling described withregard to FIG. 3, can be employed to maximize the limestone and/or oilshale formation's exposure to heat necessary to form both gaseous andliquefied hydrocarbons. It may take between 2-4 years for the formationof sufficient kerogen to be commercially recoverable. After thatrecovery may occur on a commercial level for between 3-30 years or more.

A product recovery system 160 is constructed at site 22. Productrecovery system 160 may be a conventional hydrocarbon recovery system orother suitable system that addresses the recovery requirements and iscoupled with perforation recovery wells 120 (not shown) for collectionof gaseous and liquefied hydrocarbons that are released during theretort process. An illustration of the energy flow of system 20 withretort system 120 for limestone retorting operations (FIG. 4), as shownin FIG. 5, includes nuclear energy 146 generated from nuclear reactor26. Gas is delivered from gas injection system 134 to hot gas generator128. Nuclear energy 146 creates thermal energy 132 that is transferredto hot gas generator 128 for producing hot gas 136. Hot gas 136 isdelivered to high pressure pumps 130. Pump energy 148 puts hot gas 136under high pressure.

High pressure pumps 130 deliver hot gas 136 to retort injection wells138 with sufficient energy 150 to transfer hot gas 136 to the fracturedlimestone formations for heat inducement for retort operations. Theexposure of the limestone to heat in connection with high pressureaccelerates the maturation of the hydrocarbon precursors, such askerogen, which forms liquefied and gaseous hydrocarbons. During theretort operations, hydrocarbon products 162 accumulate. Hydrocarbonproducts 162 are extracted and collected by product recovery system 160.Residual gas from the retorting operations is recovered via a gasrecycle system 145 and reinjected to hot gas generator 128 via gasinjection system 134. It is envisioned that a gas recovery system isemployed to minimize the consumption of gas used to retort the fracturedlimestone formation.

In an alternate embodiment, as shown in FIG. 6, system 20 includes aretort system 220 for retort operations relating to the fracturedlimestone formations at site 22, similar to those described. Site 22 isprepared for installation and related construction of retort system 220,which includes a steam generator and thermal transfer system components,as will be described.

Retort system 220 employs heat generated by electric heaters insertedinto holes drilled into the fractured limestone formations of site 22.The heat generated induces heating of the fractured limestone formationsto accelerate the maturation process of hydrogen precursors, asdiscussed. Nuclear reactor 26 discussed above, is a thermal source thatcooperates with a steam generator 228 to power a steam turbine 230 forgenerating steam that may be used to drive an electric generator 234 toproduce the electric energy to retort the fractured limestone formationin-situ. If a conventional pressurized water reactor or similarnon-boiling water reactor is used, a heat exchanger (not shown) may berequired. Nuclear reactor 26 is sized to be located at or near site 22of the fractured limestone formation. It is envisioned that the electriccapacity rating of nuclear reactor 26 is between 50 MWe to 2000 MWe. Itis contemplated that the hydrogen generated by nuclear reactor 26 can beused to enhance the value of carbon bearing material, which may resemblechar, so it will be recoverable. A hydrogen generator (not shown),either electrolysis, thermal or other may be attached to the nuclearreactor 26 to generate hydrogen for this use.

Water supply 34 delivers water to steam generator 228, which isconstructed and installed at site 22. Nuclear reactor 26 is coupled tosteam generator 228, as is known to one skilled in the art, for thetransfer of thermal energy 232. System 20 employs steam generator 228,in cooperation with nuclear reactor 26 as the thermal source, to producesteam 236 to activate steam turbine 230 for operating an electricgenerator to provide electric energy for the retort of the fracturedlimestone formations. If a conventional pressurized water reactor orsimilar non-boiling water reactor is used a heat exchanger (not shown)may be required.

Steam generator 228 is coupled to steam turbine 230, in a manner as isknown to one skilled in the art. Steam 236 from steam generator 228flows into steam turbine 230 to provide mechanical energy 237 to anelectric generator 234. Steam turbine 230 is coupled to electricgenerator 234, in a manner as is known to one skilled in the art, andmechanical energy 237 generates current 239 from electric generator 234.It is contemplated that current 239 may include alternating current ordirect current.

Current 239 from electric generator 234 is delivered to limestone assetelectric heating retort injection wells 238. Injection wells 238 employelectric resistance heaters (not shown), which are mounted with holesdrilled into the fractured limestone formations of site 22, to promotethe retort of the limestone. The electric resistance heaters heat thesubsurface of fractured limestone formations to approximately 343degrees C. (650 degrees F.) over a 3 to 4 year period. Upon duration ofthis time period, production of both gaseous and liquefied hydrocarbonsare recovered in a product recovery system 260.

Product recovery system 260 is constructed at site 22. Product recoverysystem 260 is coupled with injection wells 238 or perforation recoverywells for collection of gaseous and liquefied hydrocarbons that arereleased during the retort process. An illustration of the energy flowof system 20 with retort system 220 (FIG. 6) for limestone retortingoperations, as shown in FIG. 7, includes nuclear energy 246 generatedfrom nuclear reactor 26. Nuclear energy 246 creates thermal energy 232that is transferred to steam generator 228 for producing steam 236. If aconventional pressurized water reactor or similar non-boiling waterreactor is used a heat exchanger (not shown) may be required. Steam 236is delivered to steam turbine 230, which produces mechanical energy 237.Mechanical energy 237 generates current 239 from electric generator 234.

Current 239 delivers electric energy 241 to the electric heatingelements to heat the fractured limestone formations for heat inducement.The exposure of the limestone to heat accelerates the maturation of thehydrocarbon precursors, such as kerogen, which forms liquefied andgaseous hydrocarbons. During the retort operations, hydrocarbon productsaccumulate. The hydrocarbon products are extracted and collected byproduct recovery system 260. Alternatively, retort system 220, productrecovery system 260, and related components may be employed withlimestone and oil shale formation applications, or only oil shale.

In another alternate embodiment, as shown in FIG. 8, system 20 includesa retort system 320 for retort operations relating to the fracturedlimestone formations at site 22, similar to that described. Site 22 isprepared for installation and related construction of retort system 320,which includes a molten salt or liquid metal generator, bayonet heatersand thermal transfer system components, which will be described.

Retort system 320 employs molten salts or liquid metal, which areinjected into the fractured limestone formations to accelerate thematuration process of hydrocarbon precursors as discussed. Nuclearreactor 26 is a thermal source that provides thermal energy 332 toretort the fractured limestone formation in-situ. Nuclear reactor 26 issized to be located at or near site 22 of the fractured limestoneformation. It is envisioned that the thermal rating of nuclear reactor26 is between 20 MWth to 3000 MWth. It is further contemplated thathydrogen generated by nuclear reactor 26 can be used to enhance thevalue of carbon bearing material, which may resemble char and berecoverable. A hydrogen generator (not shown), either electrolysis,thermal or other may be attached to the nuclear reactor 26 to generatehydrogen for this use.

A salt injection system 334 is installed at site 22. Salt injectionsystem 334 delivers salts to a molten salt generator 328. Molten saltgenerator 328 is constructed and installed at site 22. Nuclear reactor26 is coupled to molten salt generator 328, as is known to one skilledin the art, for the transfer of thermal energy 332. System 20 employsmolten salt generator 328, in cooperation with nuclear reactor 26 as thethermal source, to produce molten salt 336 for retort of the fracturedlimestone formations.

It is envisioned that the thermal output of nuclear reactor 26 can beused to heat various types of salts for injection to retort thelimestone, such as halide salts, nitrate salts, fluoride salts, andchloride salts. It is further envisioned that liquid metals may be usedwith retort system 320 as an alternative to salts, which includes theuse of a metal injection system and a liquid metal generator. Thethermal output of nuclear reactor 26 can be used to heat various typesof metals for injection to retort the limestone, including alkali metalssuch as sodium.

Pumps 330 are installed at site 22 and coupled to molten salt generator328 for injecting molten salt 336 into the fractured limestoneformations. Pumps 330 are coupled to limestone asset heating retortinjection wells 338 to deliver molten salt 336 for the retort of thefractured limestone formations. It is envisioned that system 20 mayinclude various pump configurations including multiple pumps to maximizethe effectiveness of the retort operation. It is further envisioned thatpumps 331 may be employed to recover residual molten salt, after retortoperations, for return to molten salt generator 328, as part of therecovery and recycling system of retort system 320 discussed below.

Limestone asset heating retort injection wells 338 are installed withthe infrastructure of system 20, as discussed. Molten salt 336 istransferred to injection wells 338 and injected into the fracturedlimestone formation. The use of horizontal drilling described withregard to FIG. 3, can be employed to maximize the limestone formationexposure to heat necessary to form both gaseous and liquefiedhydrocarbons. It may take between 2-4 years for the formation ofsufficient kerogen to be commercially recoverable. After that recoverymay occur on a commercial level for between 3-30 years or more.

A product recovery system 360 is constructed at site 22. Productrecovery system 360 may be coupled with injection wells 338 forcollection of gaseous and liquefied hydrocarbons that are releasedduring the retort process or may be perforation recovery wells. Anillustration of the energy flow of system 20 with retort system 320(FIG. 8) for limestone retorting operations, as shown in FIG. 9,includes nuclear energy 346 generated from nuclear reactor 26. Salt isdelivered from salt injection system 334 to molten salt generator 328.

Nuclear energy 346 creates thermal energy 332 that is transferred tomolten salt generator 328 for producing molten salt 336. Molten salt 336is delivered to pumps 330 and pump energy 348 delivers molten salt 336to retort injection wells 338 with sufficient energy 350 to transfermolten salt 336 to the fractured limestone formations for heatinducement. The exposure of the limestone to heat accelerates thematuration of the hydrocarbon precursors, such as kerogen, which formsliquefied and gaseous hydrocarbons. During the retort operations,hydrocarbon products 362 accumulate. Hydrocarbon products 362 areextracted and collected by product recovery system 360. Residual moltensalt 364 from the retorting operations are recovered via a salt recoverysystem 345 and reinjected to molten salt generator 328 via pumps 331 andsalt injection system 334. It is envisioned that salt recovery system345 is employed to minimize the consumption of salt used to retort thefractured limestone formation. Alternatively, retort system 320, productrecovery system 360 and related components may be employed withlimestone and oil shale formation applications, or only oil shale.

In another alternate embodiment, as shown in FIG. 10, system 20 includesa retort system 420 for retort operations relating to the fracturedlimestone formations at site 22, similar to those described. Site 22 isprepared for installation and related construction of retort system 420,which includes a steam generator, oscillators and thermal transfersystem components, as will be described.

Retort system 420 employs heat generated by oscillators, which aremounted with the fractured limestone formations of site 22. The heatgenerated induces heating of the fractured limestone formations toaccelerate the maturation process of hydrogen precursors, as discussed.Nuclear reactor 26 discussed above, is a thermal source that cooperateswith a steam generator 228 to power a steam turbine 230 for generatingthe electric energy to retort the fractured limestone formation in-situ.Nuclear reactor 26 is sized to be located at or near site 22 of thefractured limestone formation. It is envisioned that the electriccapacity rating of nuclear reactor 26 is between 50 MWe to 3000 MWe. Itis contemplated that the hydrogen generated by nuclear reactor 26 can beused to enhance the value of carbon bearing material, which may resemblechar, so it will be recoverable. A hydrogen generator (not shown),either electrolysis, thermal or other may be attached to the nuclearreactor 26 to generate hydrogen for this use.

Water supply 34 delivers water to steam generator 228, which isconstructed and installed at site 22. Nuclear reactor 26 is coupled tosteam generator 228, in a manner as is known to one skilled in the art,for the transfer of thermal energy 232. System 20 employs steamgenerator 228, in cooperation with nuclear reactor 26 as the thermalsource, to produce steam 236 to activate steam turbine 230 for retort ofthe fractured limestone formations.

Steam generator 228 is coupled to steam turbine 230, in a manner as isknown to one skilled in the art. Steam 236 from steam generator 228flows into steam turbine 230 to provide mechanical energy 237 to anelectric generator 234. Steam turbine 230 is coupled to electricgenerator 234, and mechanical energy 237 generates current 239 fromelectric generator 234. It is contemplated that current 239 may includealternating current or direct current.

Current 239 from electric generator 234 is delivered to oscillators 438.The electric power delivered to oscillators 438 via current 239 createsa radio frequency having a wavelength where the attenuation iscompatible with the well spacing to provide substantially uniform heat.

A product recovery system 460 is constructed at site 22. Productrecovery system 460 is connected with the recovery wells for collectionof gaseous and liquefied hydrocarbons that are released during theretort process. An illustration of the energy flow of system 20 withretort system 420 (FIG. 10) for limestone retorting operations, as shownin FIG. 11, includes nuclear energy 446 generated from nuclear reactor26. Nuclear energy 446 creates thermal energy 232 that is transferred tosteam generator 228 for producing steam. Steam 236 is delivered to steamturbine 230, which produces mechanical energy 237. Mechanical energy 237generates current 239 from electric generator 234.

Current 239 delivers electric energy to oscillators 438 to create radiofrequencies 241 to heat the fractured limestone formations for heatinducement. The exposure of the limestone to heat accelerates thematuration of the hydrocarbon precursors, such as kerogen, which formsliquefied and gaseous hydrocarbons. During the retort operations,hydrocarbon products accumulate. The hydrocarbon products are extractedand collected by product recovery system 460. Alternatively, retortsystem 420, product recovery system 460 and related components may beemployed with limestone and oil shale formation applications, or onlyoil shale.

It will be understood that various modifications may be made to theembodiments disclosed herein. Therefore, the above description shouldnot be construed as limiting, but merely as exemplification of thevarious embodiments. Those skilled in the art will envision othermodifications within the scope and spirit of the claims appended hereto.

1. A method for recovering hydrocarbon products, the method comprisingthe steps of: producing thermal energy using a nuclear reactor;providing said thermal energy to a supercritical material generator;providing a material to said supercritical material generator; producinga supercritical material flow from said supercritical material generatorusing a high pressure pump; injecting said supercritical material flowinto fracturing wells wherein said fracturing wells are disposed in anlimestone formation; and fracturing said limestone formation using heatof said supercritical material flow from said fracturing wells.
 2. Amethod as recited in claim 1, further comprising the steps of: providingsaid thermal energy to a hot gas generator; providing a gas to said hotgas generator; producing a high pressure hot gas flow from said hot gasgenerator using a high pressure pump; and injecting said high pressurehot gas flow into injection wells wherein said injection wells aredisposed in said limestone formation.
 3. A method as recited in claim 2,further comprising the steps of: retorting limestone in said limestoneformation using heat from said hot gas flow to produce hydrocarbonproducts; and extracting said hydrocarbon products from said injectionwells.
 4. A method as recited in claim 3, wherein the step of extractingincludes a product recovery system coupled to said injection wells in aconfiguration for collection of gaseous and liquefied hydrocarbonsreleased during the step of retorting.
 5. A method as recited in claim3, further comprising the step of recovering residual gas from the stepof retorting via a recycle system, said residual gas being injected withsaid hot gas generator.
 6. A method as recited in claim 1, furthercomprising the steps of: providing said thermal energy to a steamgenerator; providing water to said steam generator; producing steam fromsaid steam generator; injecting said steam into a steam turbine togenerate mechanical energy; providing said mechanical energy to anelectric generator; generating current from said electric generator fromsaid mechanical energy; and powering electric resistance heaters withsaid current, said heaters being disposed with injection wells whereinsaid injection wells are disposed in said limestone formation.
 7. Amethod as recited in claim 6, further comprising the steps of: retortinglimestone in said limestone formation using heat from said heaters toproduce hydrocarbon products; and extracting said hydrocarbon productsfrom said injection wells.
 8. A method as recited in claim 7, whereinthe step of extracting includes a product recovery system coupled tosaid injection wells in a configuration for collection of gaseous andliquefied hydrocarbons released during the step of retorting.
 9. Amethod as recited in claim 1, further comprising the steps of: providingsaid thermal energy to a molten salt or liquid metal generator;providing a salt or metal to said molten salt or liquid metal generator;producing a molten salt or liquid metal flow from said molten salt orliquid metal generator using a pump; and injecting said molten salt orliquid metal flow into bayonet injection wells wherein said injectionwells are disposed in said limestone formation.
 10. A method as recitedin claim 9, further comprising the steps of: retorting limestone in saidlimestone formation using heat from said molten salt or liquid metalflow to produce hydrocarbon products; and extracting said hydrocarbonproducts from said injection well.
 11. A method as recited in claim 10,wherein the step of extracting includes a product recovery systemcoupled to said injection wells in a configuration for collection ofgaseous and liquefied hydrocarbons released during the step ofretorting.
 12. A method as recited in claim 10, further comprising thestep of recovering residual salt or metal from the step of retorting viaa recycle system, said residual salt or metal being injected with saidmolten salt or liquid metal generator.
 13. A method as recited in claim1, further comprising the steps of: providing said thermal energy to asteam generator; providing water to said steam generator; producingsteam from said steam generator; injecting said steam into a steamturbine to generate mechanical energy; providing said mechanical energyto an electric generator; generating current from said electricgenerator from said mechanical energy; and powering oscillators withsaid current to create radio frequencies to produce heat, saidoscillators being disposed with injection wells wherein said injectionwells are disposed in said limestone formation.
 14. A method as recitedin claim 13, further comprising the steps of: retorting limestone insaid limestone formation using heat from said oscillators to producehydrocarbon products; and extracting said hydrocarbon products from saidinjection wells.
 15. A method as recited in claim 13, wherein the stepof extracting includes a product recovery system coupled to saidinjection wells in a configuration for collection of gaseous andliquefied hydrocarbons released during the step of retorting.
 16. Amethod as recited in claim 1, further comprising the step ofconstructing an infrastructure in said limestone formation, saidinfrastructure being formed by horizontal and vertical directiondrilling in a configuration to increase permeability and porosity ofsaid limestone formation.
 17. A method for recovering hydrocarbonproducts, the method comprising the steps of: producing thermal energyusing a nuclear reactor; providing said thermal energy to a hot gasgenerator; providing a gas to said hot gas generator; producing a highpressure hot gas flow from said hot gas generator using a high pressurepump; injecting said high pressure hot gas flow into injection wellswherein said injection wells are disposed in an limestone formation;retorting limestone in said limestone formation using heat from said hotgas flow to produce hydrocarbon products; and extracting saidhydrocarbon products from said injection wells.
 18. A method forrecovering hydrocarbon products, the method comprising the steps of:producing thermal energy using a nuclear reactor; providing said thermalenergy to a steam generator; providing water to said steam generator;producing steam from said steam generator; injecting said steam into asteam turbine to generate mechanical energy; providing said mechanicalenergy to an electric generator; generating current from said electricgenerator from said mechanical energy; powering electric resistanceheaters with said current, said heaters being disposed with injectionwells wherein said injection wells are disposed in an limestoneformation; retorting limestone in said limestone formation using heatfrom said heaters to produce hydrocarbon products; and extracting saidhydrocarbon products from said injection wells.
 19. A method forrecovering hydrocarbon products, the method comprising the steps of:producing thermal energy using a nuclear reactor; providing said thermalenergy to a molten salt or liquid metal generator; providing a salt ormetal to said molten salt or liquid metal generator; producing a moltensalt or liquid -metal flow from said molten salt or liquid metalgenerator using a pump; injecting said molten salt or liquid metal flowinto bayonet injection wells wherein said injection wells are disposedin an limestone formation; retorting limestone in said limestoneformation using heat from said molten salt or liquid metal flow toproduce hydrocarbon products; and extracting said hydrocarbon productsfrom said injection well.
 20. A method for recovering hydrocarbonproducts, the method comprising the steps of: producing thermal energyusing a nuclear reactor; providing said thermal energy to a steamgenerator; providing water to said steam generator; producing steam fromsaid steam generator; injecting said steam into a steam turbine togenerate mechanical energy; providing said mechanical energy to anelectric generator; generating current from said electric generator fromsaid mechanical energy; powering oscillators with said current to createradio frequencies to produce heat, said oscillators being disposed withinjection wells wherein said injection wells are disposed in a limestoneformation; retorting limestone in said limestone formation using heatfrom said oscillators to produce hydrocarbon products; and extractingsaid hydrocarbon products from said injection wells.
 21. A method asrecited in claim 1, wherein the step of injecting includes saidfracturing wells being disposed in a formation including limestone andoil shale.
 22. A method as recited in claim 3, wherein the step ofretorting includes retorting oil shale and limestone.